1. Field
The present invention relates to a water-and-hot-water mixing device for obtaining mixed water of an adjusted temperature by mixing hot water and water supplied to the water-and-hot-water mixing device by way of predetermined flow passages.
2. Description of the Related Art
In general, for example, a washbowl cabinet or the like is provided with a water-and-hot-water mixing device for obtaining mixed water of an adjusted temperature. According to such a water-and-hot-water mixing device, hot water and water supplied by way of predetermined flow passages are mixed together and mixed water whose temperature is adjusted is supplied to a faucet body provided to a washbowl cabinet or the like. That is, with respect to mixed water which is discharged from a spout of the faucet body, the adjustment of temperature and flow rate and the changeover of discharge/stop of water (flow-out and stop of flow-out of water or hot water) are performed by the water-and-hot-water mixing device. Here, the adjustment of temperature and flow rate of mixed water discharged from the spout of the faucet body, and the changeover of discharge/stop of water are performed by operating an operation part arranged in the vicinity of the faucet body provided to the water-and-hot-water mixing device or the like.
Such a water-and-hot-water mixing device includes a mixing valve unit which suitably mixes hot water supplied by way of a hot water supply pipe connected to a hot water supply device and water supplied by way of a water supply pipe communicated with a service water pipe for controlling a temperature of mixed water. On a downstream side (downstream) of the mixing valve unit, an open/close flow rate adjusting valve which performs the open/close flow rate adjustment is arranged. The water-and-hot-water mixing device is also configured to discharge mixed water of a predetermined temperature from the faucet body due to an operation of an open/close flow-rate adjusting valve. That is, in the water-and-hot-water mixing device, the mixing valve unit is driven by an operation part via a predetermined control part so as to perform the water-and-hot-water mixing adjustment to obtain water of an appropriate temperature; and a flow rate of mixed water to be discharged is adjusted to a predetermined flow rate by a fixed flow rate adjusting part. Due to such an operation, the discharge of mixed water of a predetermined temperature and a predetermined flow rate from the faucet body becomes possible. The mixing valve unit is associated with temperature adjustment of mixed water by operating a valve element for adjusting opening of inlet for hot water and opening of inlet for water. The valve element provided to the mixing valve unit is operated by an electric drive source such as a motor.
The water-and-hot-water mixing device also includes the following constitution. That is, for adjusting the predetermined temperature of hot water supplied from the hot water supply device, to a middle portion of the hot water supply pipe connected to the hot water supply device, a supplied hot water temperature detector such as a thermistor which detects a temperature of hot water supplied from the hot water supply device is provided. Further, in a middle portion of a water discharge pipe between the fixed flow rate adjusting part and the faucet body, a mixed water temperature detector such as a thermistor which detects a temperature of mixed water is provided. These supplied hot water temperature detector and the mixed water temperature detector are connected to the control part. Further, the control part is connected to a drive source of the mixing valve unit and a flow rate adjusting device for performing the flow rate adjustment. Due to such a constitution, the water-and-hot-water mixing device is configured to perform mixing of water and hot water and the adjustment of the discharge water flow rate by driving the respective devices in response to instructions from the control part.
Then, in the water-and-hot-water mixing device which includes such a mixing valve unit, a feedback control is applied to discharge water temperature (temperature of mixture of water and hot water produced by the mixing valve unit). In this feedback control, the control part performs the comparison calculation of data from the mixed water temperature detector and data on a target temperature (temperature set by the operation part). Based on the result of the comparison calculation, the mixing valve unit is driven in response to instructions outputted from the control part, mixed water of predetermined appropriate temperature is discharged from the faucet body. To be more specific, in the feedback control of the discharge water temperature, the discharge water temperature is detected by the mixed water temperature detector. Then, the detected discharge water temperature is compared with the target temperature, and the mixing valve unit is controlled based on the difference between the detected discharge water and the target temperature. That is, in the mixing valve unit, the drive source such as the motor is controlled corresponding to a magnitude of the difference between the detected discharge water temperature and the target temperature so that the valve element is moved so as to eliminate a gap between the detected discharge water temperature and the target temperature. Due to such a feedback control, the discharge water temperature is constantly corrected aiming at the target temperature.
As the water-and-hot-water mixing device which performs such a feedback control, there has been known a water-and-hot-water mixing device described in JP-A-5-233075 (patent document 1), for example. In the water-and-hot-water mixing device described in patent document 1, when hot water is again supplied from a hot water supply device for discharging mixed water again from a faucet body, data on temperature of supplied hot water detected by a supplied-hot-water temperature detector in a previous hot-water discharge time is constantly stored in a control part, and a water-and-hot-water mixing ratio of a mixing valve unit is maintained in a previous stopped state until the data on temperature of supplied hot water approaches newest updated data or until a preliminarily set fixed time elapses irrelevant to monitoring of the newest updated data. Thereafter, the water-and-hot-water mixing device performs a feedback control using a mixed water temperature detector such as a thermistor.
However, in the water-and-hot-water mixing device described in patent document 1, particularly, when the set temperature of the hot water supply device is set to a temperature lower than the set temperature set in the previous hot water discharge time, eventually, the water-and-hot-water mixing ratio is maintained in the previously set state within a fixed time. Accordingly, a feedback control is not started unless the fixed time elapses so that a temperature adjustment time is prolonged thus giving rise to a drawback that the temperature adjustment becomes cumbersome. That is, in the water-and-hot-water mixing device described in patent document 1, at the time of supplying hot water from the hot water supply device again, the water-and-hot-water mixing ratio of the mixing valve unit is maintained in a previous stopped state until the data on temperature of supplied hot water approaches newest updated data at the previous time of supplying hot water or until a preliminarily set fixed time elapses irrelevant to monitoring of the newest updated data. From above, in spite of a fact that the temperature of hot water supplied again is set lower than the temperature at the previous hot water discharge so that the temperature of supplied hot water supplied from the hot water supply device becomes a temperature which substantially corresponds to the predetermined temperature and is stable originally, a control of discharge water temperature by a feedback control is not performed until a fixed standby time elapses. As a result, there arises a drawback that a temperature adjustment start time is delayed.
Further, conventionally, the mixing valve unit is constituted of a valve element which moves in a mixing valve casing so as to change a flow rate of hot water and a flow rate of water, and a valve drive mechanism which drives the valve element. The mixing valve unit discharges mixed water of predetermined temperature by performing a feedback control of the valve drive mechanism. In such a mixing valve unit having the above-mentioned constitution, when high-temperature hot water is suddenly supplied from the hot water supply device before the feedback control is performed, the feedback control is not performed in time thus giving rise to a possibility that an overshoot phenomenon where high-temperature mixed water is discharged from the mixing valve unit occurs.